This is not a comprehensive document regarding comma rules. The comma rules listed here are the most common errors found in writing. Other comma rules exist and can be found in an English handbook or online.
Rule No. 1: Coordinating Conjunctions and Commas
Compound sentence structures include a sentence + a coordinating conjunction + another sentence. It requires a comma before the coordinating conjunction (and, but, for, or, nor, so, yet). Put your finger on the conjunction in the sentences below, and see if a sentence can be found on both sides of it. If the conjunction joins two sentences, then you need a comma before the conjunction. If one side is not a sentence, then a comma is not placed before the coordinating conjunction.
I called my friend Ginny, and she agreed to meet me after work.
I called our plumber Jack, but he was unable to help me fix our leaky faucet.
Use the Search/Find Tool to find the coordinating conjunctions in your writing:
Rule No. 2: Subordinating Conjunctions and Commas
If a sentence begins with a subordinate conjunction, then it needs a comma after the introductory phrase. See the list below for subordinating conjunctions. Notice in the sentences below, the comma is in the middle of the sentence between the introductory phrase and the main part of the sentence. It is not directly after the subordinating conjunctions.
After Ginny and I had supper together, we went to a movie.
When Jack couldn’t fix our leaky faucet, we called Henry.
Use the Search/Find Tool to find the subordinating conjunctions in your writing:
- According to
- As soon as
- By the time
- Even if
- Even though
- In case
- In order that
- Just in case
- Whether or not
Rule No. 3: Lists of Nouns and Adjectives and Commas
When three or more nouns appear in a list in a sentence, they need commas. When three or more adjectives appear in a list in a sentence, they need commas. Without commas, meaning can be misunderstood.
Mikayla likes eating fish, salads, and vegetables.
She is talkative, kind, and thoughtful.
Use the Search/Find Tool to find the connecting words used in lists:
Rule No. 4: Transitional Words and Commas
Some transitional words require commas no matter where they appear in sentences.
If the transitional word is at the beginning of the sentence, the comma comes after it.
However, your answer is incorrect.
If the transitional word is at the end of the sentence, the comma comes before it.
Your answer is incorrect, however.
If the transitional word is in the middle of the sentence, commas go on both sides of the transitional word(s).
Your answer, however, is incorrect.
Use the Search/Find Tool to find the following transitional words and phrases:
- As a result
- For example
- For instance
- For this purpose
- For this reason
- In addition
- In conclusion
- In contrast
- In fact
- In other words
- In summary
- On the one hand
- On the other hand
- To sum up
- To summarize